Second-seeded Viktor Troicki saw off qualifier Daniel Brands to join top seed Roberto Bautista-Agut in the Sofia Open quarter-finals.
Serbia's Troicki defeated Brands 6-4 6-3 to set up a last-eight meeting with another German in fifth seed Philipp Kohlschreiber, who beat Damir Dzumhur of Bosnia and Herzegovina 6-1 4-6 6-3.
Bautista-Agut advanced when Filip Krajinovic pulled out of their second-round match before it started because of a shoulder problem.
The Spaniard will now play eighth seed Adrian Mannarino, victor in round two against Marius Copil.
Fourth seed Andreas Seppi and sixth seed Gilles Muller also made it through to the quarters via triumphs over Thiemo De Bakker and Ricardas Berankis on Thursday respectively.
Source: PA
